Java Programming

Are +"Xss" +"ThreadStackSize" the same? ... I've googled stuff back to 2006 and no one answers this very well.

I did find one good clue (that I'd never heard before) on an Oracle site: It said, "A special system stack size is used for JVM internal threads; for example, the garbage collection and code generation threads. The default system stack size is 256 KB on all platforms. Note: The -Xss command line option sets the stack size of *both application threads and JVM internal threads*."

Nowhere else is this mentioned. i.e., that there is a differentiation between the default size of system threads and applications threads.

So what does ThreadStackSize set? Just application threads?
Sadly, the first hit, when googling +"Xss" +"ThreadStackSize" turns an article that is ages old, talking only about VMs up to 1.4: http://java.sun.com/docs/hotspot/threads/threads.html

Also, could someone explain...(for solaris systems)
Do ThreadStackSize threads reside in the heap itself, and Xss (system) threads reside in the unix-process memory space outside the heap?

Or do I have this all wrong? Thanks.